Acquisitions and Dispositions - Southern Company Narrative (Details) - Subsequent Event - USD ($) $ in Millions		3 Months Ended
Oct. 29, 2021	Dec. 31, 2021
Lessor, Lease, Description [Line Items]
Proceeds from sale of assets subject to leveraged lease	$ 45
Scenario, Forecast
Lessor, Lease, Description [Line Items]
Leveraged leases, income tax benefits		$ 16

Amount of investment tax credit recognized as income.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 50
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123416469&loc=SL77920237-209979

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=123394354&loc=d3e45152-112736

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration